Rapid tire deflation system

ABSTRACT

A central tire deflation system for emergency vehicles, such as fire trucks, rescue vehicles located at airports, enabling the operator to deflate all of the tires of the emergency vehicle to a predetermined minimum pressure while traveling to a crash site so that the &#34;footprint&#34; of the tires is increased at or about the time the vehicle reaches soft terrain. The minimum tire pressure is obtained by controlling the duration of time that the tires are being deflated.

This is a continuation of co-pending application serial no. 07/142,599filed on Jan. 11, 1988, now abandoned.

This invention relates to a rapid tire deflation system for emergencyvehicles such as ambulances, fire trucks, rescue vehicles and the likeparticularly those existing at airports and used to fight fires andrescue victims of air crashes located on or nearby the airport. Suchemergency vehicles must have the capability of traveling as quickly aspossible over paved runways, roads and the like and the capability oftraveling as quickly as possible over soft terrain such as mud, sand,snow and the like.

It is well known that the traction of vehicles on soft terrain maygreatly improve by decreased inflation pressure within the tires andthus increased contact area between the tires and terrain. Central tireinflation/deflation systems are also known, particularly for militaryvehicles as may be seen by reference to U.S. Pat. Nos. 4,690,3312,634,781 and 3,361,180, which are hereby incorporated by reference.Such systems are known as central tire inflation systems (CTIS) whichallow the operator to remotely, manually and/or automatically varyand/or maintain the inflation pressure of one or more of the vehicletires utilizing an on board source of pressurized fluid (usuallycompressed air from the vehicle air brake compressor and/or a compressedair reservoir) and are quite satisfactory for vehicles such as militaryvehicles which may utilize the CTIS over varying conditions of terrain.

However, these prior art systems are not satisfactory for the aforesaidemergency vehicles since they include an inflation system as well as adeflation system for the tires, are relatively slow in inflating ordeflating the tires and are relatively expensive to install andmaintain.

U.S. Pat. No. 3,361,180 discloses a tire deflating system for militaryaircraft, including an electrically actuated tire valve, which willenable the aircraft to take off fully loaded with the tires fullyinflated and which will allow the tires to be partially deflated inflight to a predetermined lower pressure to enable the aircraft to landon an unprepared field or sandy desert. The electrically actuated tirevalve requires three sets of brushes and commutator rings to energizethe tire valve. The system is likewise slow acting, relatively expensiveand difficult to maintain.

Accordingly, it is an object of this invention to provide a tiredeflation system wherein the pressures in all of the tires of anemergency vehicle may b readily and quickly deflated to a predeterminedminimum pressure while nearing the end of a hard surfaced, road orrunway so that the "footprint" of the tires is increased at or about thetime the vehicle reaches soft terrain to enable the vehicle to reach thesite of a crash as quickly as possible.

Another object of the invention is to provide a novel tire deflationsystem for emergency vehicles whereby a minimum pressure of the deflatedtires is obtained by controlling the duration of time that the tires arebeing deflated.

This and other objects and advantages of the present invention willbecome apparent from a reading of the following description of thepreferred embodiment taken in connection with the attached drawings.

FIG. 1 is a schematic illustration of the pneumatic components of thepresent invention as utilized to control the deflation of the tires ofan emergency vehicle.

FIG. 2 is a sectional view of the normally closed wheel valve.

In accordance with this invention all of the tires 12 of emergencyvehicles as described above are deflated substantially, simultaneouslyand rapidly by the deflation system 10 shown in FIG. 1. The inflatabletires 12 are each mounted on a tire rim 14 which is fixed to a wheel hubassembly 16 rotatably supported on the outer end of an axle housing 18by means of bearings 20. An annular sleeve 24 is pressed fitted to theaxle at a location inboard of the bearings 20. The wheel hub is providedwith an inwardly extending sleeve type annular flange 26 telescopicallysurrounding sleeve 24. A pair of rotary seals 28 and 30 extend radiallybetween the outer periphery of sleeve 24 and the inner periphery ofsleeve type flange 26 to define an annular seal chamber 32 therebetween,as may be seen in greater detail by reference to U.S. Pat. No.4,434,834, assigned to the assignee of this invention. Sleeve 24 isprovided with an inlet 34 and a passage 36 opening to the chamber 32.The sleeve type flange 26 is provided with a generally radiallyextending passage 38 extending from the sealed chamber 32 to theexterior outer diameter surface thereof. A single passage 40 may beprovided in the radial flange portion 42 of the wheel hub 16 for passageof a pressure conduit 44.

The pressure conduit 44 is connected to the inlet 46 of the tire controlvalve 48 mounted on the wheel hub 16. The valve 48 has a port 50connected by a pressure conduit 52 to the interior chamber 54 of thetire 12. A manual inflate and check valve 56 may be connected to theconduit 52 or directly through the rim 14 to the tire chamber 54.

As may be seen by reference to FIG. 2, the wheel valve 48 is an airactuated normally closed valve. The valve 48 defines three ports, port50 connected by conduit 52 to the tire chamber 54, port 46 connected tothe sealed chamber 32 and port 58 connected to the exhaust conduit 60which is vented to atmosphere. Valve 48 includes a tubular body 62sealed by end plugs 64 and 65. An annular valve seat 68 is positionedbetween the ports 50 and 58. A valve member 70 having a valve seat 72 isurged by compression spring 74 into sealing engagement against the seat68. The plug 64 includes a projection 76 partially extending into ablind hole in the valve member 70 forming a cavity 78 to retain thespring 74. Accordingly, the valve 48 is normally held in closed positionto prevent air from escaping from the conduit 52 to the exhaust conduit60.

The valve 48 is opened by pressurized air entering port 46 to actuatethe piston 80 to thereby move the piston and the projection 82 towardthe valve member 70 so that the valve seat 72 thereof is moved off ofthe valve seat 68 against the bias of spring 74. The valve seats 72 and68 are thus unsealed and moved apart far enough to permit free flow andrapid exhaust of air from the tire 12 to the conduit 60. While thestructure of valve 48 has been described with a certain degree ofdetail, it is understood that air actuated valves performing the samefunction, but of different construction, may be substituted therefor.

Each of the wheel assemblies 16 of the emergency vehicle is providedwith a wheel valve 48 each supplied with actuating pressurized air froma common source 84 which is typically a pressurized air reservoirsupplied by a compressor. The pressurizing air source 84 is connected toinlet 86 of a dual shut-off and exhaust valve 88 by a conduit 90. Theoutlet 92 of valve 88 is connected to a manifold 94 and is normallyconnected to the port 100 of the exhaust conduit 102. A plurality ofconduits 104 connect the manifold 94 to each of the inlets 34, sealedchamber 32, conduits 44 and hence to the wheel valves 48 on each wheelof the vehicle.

The shut-off and exhaust valve 88 has a first or normal position, asshown in FIG. 1, blocking the flow of air between the inlet 86 andoutlet 92 thereof, and a second or open position permitting air flowbetween the inlet 86 and outlet 92 thereof. The valve 88 is electricallyoperated and preferably a solenoid controlled valve of conventionaldesign spring biased to the normal position shown in FIG. 1. In thenormal closed position outlet 100 is open to exhaust air to the exhaust102 from the manifold 94 and the air circuit to each wheel valve 48.

The solenoid 106 of the valve 88 is connected to a "deflate" push buttonswitch 108 mounted on the control panel 110 located in the cab of thevehicle. An on/off switch 112 and a timer 114 with a screw operatedadjusting means 116 are also mounted on the control panel 110 andconnected to a battery 118. The timer adjusting means 116 is initiallymanually adjusted so that the timer clock therein is set to run for apredetermined period of time necessary to deflate the tires 12 from anormal over the road operating pressure of, for example 60 psi, to alower pressure, for example 20 psi, for operation over soft terrain suchas mud, sand, snow or the like. The duration of time that the timerclock is set to run depends on the initial tire pressure, the tire sizeand the size of the passages and ports in the conduit 52 and wheel valve48 mounted on each wheel 16. Generally, the timer adjusting means 116 ismanually set so that the timer 114 operates for a duration of between afew seconds and 30 seconds corresponding to the time necessary to lowerthe tire pressure from its normal operating pressure to a minimumpressure for most efficiently operating over soft terrain.

Assuming that an emergency vehicle, equipped with the tire deflationsystem of this invention, is stationed at an airport and an air crashoccurs nearby in soft terrain some distance from the end of the runway.The vehicle can travel at top speed down the runway with the tiresinflated at normal pressure. As the vehicle approaches the end of therunway the operator turns the switch 112 to the "on" position. As thevehicle approaches soft terrain, the operator pushes the "deflate" pushbutton 108 energizing the solenoid 106 of the valve 88 and starts thetimer 114. The solenoid 106 moves the valve 88 to open the inlet 86 andoutlet 92 so that pressurized air from the air source 84 flows into themanifold 94 and the air circuit to open the normally closed wheel valves48. At the same time, the outlet port 100 of the solenoid valve 88 isclosed. The wheel valves 48 are all kept open so long as the air circuitto the valves 48 is pressurized. After the timer 114 has operated forthe predetermined period of time, the solenoid 106 of the solenoid valveis deenergized and the valve 88 is moved to its normal deactivatedposition shown in FIG. 1. The air circuit to the wheel valve 48 isdepressurized and each of the wheel valves move to the closed positionshown in FIG. 2 with the pressure of each tire lowered to apredetermined minimum pressure for traveling over soft terrain whichoccurs at or about the same time the vehicle reaches soft terrain.

Accordingly, this invention provides a tire deflation system for rapidlydeflating all of the tires of an emergency vehicle which is operatorinitiated by simply pushing the push button switch 108 as the vehicleapproaches soft terrain so that all of the tires are deflated for apredetermined period of time to enable the vehicle to proceed over softterrain with a larger tire "footprint" and increased traction so thatthe vehicle can proceed to the site of a crash, or the like, as quicklyas possible.

I claim:
 1. A rapid tire deflation system for emergency vehicle tirescomprising;a plurality of wheels each provided with a pressurized tire;an air actuated two position wheel valve mounted on each wheel which isnormally closed and when opened, exhausts the pressurized air in saidtire to atmosphere; an air circuit for actuating said wheel valvesincluding conduits for communicating air between each wheel valve and asingle solenoid valve connecting said air circuit to a source ofpressurized air on said vehicle; said solenoid valve mounted on saidvehicle and energized by a manually activated switch which when actuatedenergizes said solenoid valve to pressurize said air circuit to opensaid wheel valves to deflate said tires; and an electrical controlcircuit and timer means for controlling the duration of time saidsolenoid valve is energized and said duration of time said solenoidvalve is energized being the duration of time said wheel valves areopened so that said tires are depressurized to a predetermined lowerpressure.
 2. A rapid tire deflation system for emergency vehicle tiresas claimed in claim 1 in which said control circuit maintains saidsolenoid valve in open position for a predetermined time until saidtires have been depressurized to the predetermined lower pressure.
 3. Arapid tire deflation system for emergency vehicle tires as claimed inclaim 1 in which said control circuit includes a manually actuatednormally open switch.
 4. A rapid tire deflation system for emergencyvehicle tires as claimed in claim 3 in which said control circuitincludes a push button for initiating the energization of said timer andsolenoid valve.
 5. An emergency deflation system for vehicle tires asclaimed in claim 1 in which said timer is manually adjustable toincrease or decrease the duration of time said solenoid valve isenergized, thereby controlling the lower pressure to which the tires aredeflated.
 6. A rapid tire deflation system for emergency vehicle tiresas claimed in claim 1 in which said solenoid valve is operative whende-energized to directly exhaust the pressurized air in the conduitsbetween the solenoid valve and the wheel valves.